First apologies to Kovid that I called you Kovi in the last post... And may take this chance to say Callibre is an amazing work - I can't imagine the hours you must have spent developing and supporting this... Thank you.

To theducks - I've tried looking at rights and owner with nothing obvious showing - but thanks for the suggestion.

Going back to Kovids suggestion to run the library check...
I re-ran the library check and got the same message (shown as attachment) i.e 'found no errors in Callibre library database' - however this time I went on to check that the 'files in your library match the information in your database'
This bought up the 'problems found' notification (again as attached) showing extra titles and extra authors...

This is where I'm getting stuck - if I've read the info in the Help to the right of the window correctly - after I check the boxes - pressing the 'fix' button will tell Callibre that the formats are really gone. This is not really what I want to do... (And if you notice from the attaced screen shot the 'fix' button is greyed out anyway - the only option is 'delete'). What I really want to do is tell Callibre that the formats are actually valid and please go off and re-check. Is this something I can do? Anyone have any thoughts on this? Do I need to delete the items without a format and try re-adding?